EP0548740B2 - Light-currable polymeric adhesive based on methylmethacrylate - Google Patents

Abstract

Light-curing (photocuring) adhesive for acrylic plastic mouldings, containing a solution which comprises at least 80% by weight of methyl methacrylate and a methyl methacrylate polymer, and furthermore up to 7% by weight of a crosslinking, multifunctional monomer, in particular acrylic or methacrylic monomers, and at least one daylight photoinitiator or the latter in combination with UV photoinitiators.

Description

The invention relates to a light-curable polymerization adhesive based on methyl methacrylate and the use thereof as an adhesive for molded articles made of acrylic plastic and for gluing a molded article made of acrylic plastic with a molded body made of another plastic or a different material.

State of the art

Light-curable systems based on methyl methacrylate, in addition to the monomeric methyl methacrylate compound and optionally further (meth) acrylic monomers or polymeric (meth) acrylates, in particular polymethyl methacrylate included are known. No. 3,616,367 describes systems made of methyl methacrylate / polymethyl methacrylate, which especially extruded into sheets in the extruder and with UV light in the presence of photoinitiators, especially with benzoin hardened, i.e. be polymerized.

Also adhesive for gluing molded parts made of acrylic plastic with the components methyl methacrylate, polymethyl methacrylate and photoinitiator are known. Such a light-curable adhesive with diisopropylxanthogen disulfide is marketed as a UV light initiator under the name "Acrifix® 92" (trademark of Röhm GmbH). On Improved light-curable adhesive compared to Acrifix® 92, which additionally contains 1 to 20% by weight of a cross-linking, contains multifunctional acrylic and / or methacrylic monomers is described in DE 40 00 171 A1. A Compared to Acrifix® 92, curing is relatively quick due to UV radiation in the presence of, for example, benzil dimethyl ketal achieved as a UV photoinitiator.

DE-OS 29 09 993 includes light-curable molding, impregnating and coating compositions based on monomers unsaturated polyester resins, urethane-modified unsaturated polyester resins and unsaturated vinyl ester resins, those as UV sensitizers arylphosphine oxide compounds or these in combination with aromatic ketones, such as. Contain benzil ketals and aromatic disulfides.

DE-OS 36 19 792 describes materials for the production of photoresist layers which consist of photopolymerizable unsaturated organic compounds, optionally a polymeric binder, further from photopolymerization initiator, a color former with a photo-oxidizing agent such as an acylphosphine oxide, and others Additions exist. Polymerizable unsaturated compounds include Diacrylates and triacrylates and as color formers is called Michler's ketone.

In polym. Paint Color J., 175 (4150), 636-8, 640 (1985) describes arylphosphine oxides, a new class of UV initiators, especially about 2,4,6-trimethylbenzoyldiphenylphosphine oxide as UV initiator, i.a. for acrylic paints Manufacture of coatings, reported.

With visible light, i.e. with light of wavelengths greater than 400 nm, curable systems that are generally one or containing multiple (meth) acrylate monomers usually use 2,3-bornanedione (camphorquinone) in combination with an organic amine as photoinitiator system. 2,3-Bornandion absorbs light in the wavelength range from 420 to 460 nm. In the excited triplet state of the diketone, an amine is formed to initiate the polymerization empowered ionic radical. Such systems are used in dental materials or in adhesives that are polymer-functional Contain acrylic monomers and polymers such as elastomers or polyfunctional aliphatic urethane acrylates for Connection of polycarbonate fittings used (GB 2 216 136 A).

Task and solution

The invention has for its object the known adhesives for acrylic plastics based on methyl methacrylate also with light sources that practically only visual light, i.e. those with wavelengths greater than 400 nm i.e. Daytime addiction emit, in particular light with wavelengths of 400 to 500 nm must also be present photopolymerize.

It has been found that adhesives for moldings made of acrylic plastics, which consist essentially of methyl methacrylate and a methyl methacrylate polymer are curable with daylight if the adhesive is one Contains photoinitiator I which has at least one absorption band in the wavelength range from 340 to 500 nm, in combination with other photoinitiators with at least one absorption band between 340 and 500 nm, and namely those that are emitted by light of the wavelength range of the maximum emission of common UV fluorescent tubes approx. 300 to approx. 400 µm can be excited - Photoinitiators II.

Examples of photoinitiators based on methyl methacrylate monomer / polymer in the system with methyl methacrylate, cause a daylight-initiated curing are acyldiphenylphosphine oxides, especially 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, as Lucirin® TPO (BASF) in trade or 2,3-bornanedione, also as camphorquinone or known as Camphorquinone. 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide shows in addition to one in the near UV 300 nm pronounced absorption maximum between 340 and 420 nm wide, but with a relatively low extinction height lying absorption area.

wie beispielsweise Irgacure® 369, das einen breiten UV-Absorptionsbereich von kleiner 260 nm bis in den sichtbaren Bereich von ca. 430 nm besitzt.Examples of photoinitiators II are diisopropylxanthogen disulfide with an absorption range of approximately 300 to 380 nm or a ketone derivative of the general formula

such as Irgacure® 369, which has a broad UV absorption range from less than 260 nm to the visible range of approx. 430 nm.

Photoinitiators I and Photoinitiators II are distinguished from each other by the fact that their absorption maxima are in the wavelength range from 340 to 500 nm at different wavelengths.

An initiation of the polymerization bond with a combination of photoinitiator I and photoinitiator II is particularly indicated for the production of high-quality bonds, e.g. Fillet welds for production high-quality components that must be free from shrink bubbles.

Spectroscopic measurements on the initiator combination of Lucirin® TPO (Photoinitiator I) and diisopropylxanthogen disulfide (Photoinitiator II) show that this combination of initiators compared to Lucirin® alone, in particular in the emission range of the above-mentioned UV fluorescent tubes (e.g. UV-LS tube TL 09, solarium) more absorbed.

This shows another advantage of the invention, namely a significantly reduced UV exposure when working with the combination Photoinitiator I and Photoinitiator II. When working with the combination I and II this must be clear in the long-wave range, i.e. absorb in the range greater than 380 - 400 nm in order to harden with daylight tubes or Allow room lighting, including natural ones. The daylight initiator photo initiator I. performs this task Combining the two types of photoinitiators gives the processor a wide selection of lamp types that are suitable for the Curing suitable are available.

Lichtbärtender Polymerisationsklebstoff für Acrylglas, bestehend aus einer Lösung eines mit vorwiegend aus Methylmethacrylat aufgebauten Polymeren in polymerisierbarem Monomeren, das im wesentlichen Methylmethacrylat ist,
dadurch gekennzeichnet,

daß der Anteil des Methylmethacrylat-Polymeren zwischen 20 - 60 Gew.-% bezogen auf das Gewicht des Klebmittels liegt, der Anteil des Methylmethacrylat-Polymeren zusammen mit flüssigem, monomeren Methylmethacrylat am Klebmittel wenigstens 80 Gew.-% ausmacht, und das klebmittel bis 7 Gew.-% eines vernetzenden mehrfunktionellen Monomeren enthält und

zur Photopolymerisationsauslösung eine Kombination mindestens eines Tageslicht-Photoinitiators in Mengen von 0,01 bis 10 Gew.-%, der mindestens eine Absorptionsbande im Wellenlängenbereich von 340 - 500 nm aufweist, und eines Photoinitiators II enthält, der mindestens eine Absorptionsbande im selben Wellenlängenbereich aufweist, wobei die Absorptionsmaxima der Absorptionsbanden der beiden Photoinitiatoren in diesem Wellenlängenbereich bei verschiedenen Wellenlängen liegen.

The invention relates to:

Light-curing polymerization adhesive for acrylic glass, consisting of a solution of a polymer composed predominantly of methyl methacrylate in polymerizable monomer, which is essentially methyl methacrylate,
characterized,

that the proportion of the methyl methacrylate polymer is between 20-60% by weight, based on the weight of the adhesive, the proportion of the methyl methacrylate polymer together with liquid, monomeric methyl methacrylate in the adhesive is at least 80% by weight, and the adhesive to 7 % By weight of a crosslinking multifunctional monomer and

to trigger photopolymerization, a combination of at least one daylight photoinitiator in amounts of 0.01 to 10% by weight, which has at least one absorption band in the wavelength range from 340-500 nm, and a photoinitiator II, which has at least one absorption band in the same wavelength range, the absorption maxima of the absorption bands of the two photoinitiators in this wavelength range being at different wavelengths.

The preferred combination of photoinitiator I and photoinitiator II consists of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and diisopropylxanthogen disulfide

Implementation of the invention

The adhesive preferably has a viscosity in the range of 100 to 5000 mPa · s at room temperature. At a lower viscosity there is a risk that the adhesive from the adhesive joint before or during the irradiation expires. With a higher viscosity, the application becomes more difficult. The suitable viscosity can be selected adjust the type and amount of dissolved methyl methacrylate polymer as desired

The proportion of the methyl methacrylate polymer is between 20 and 60% by weight, especially between 20 and 40 wt .-%, based on the weight of the adhesive. The molecular weight of the polymer is usually in the range of 10,000 to 1 million (weight average).

The methyl methacrylate polymer is 40 to 100%, preferably 90 to 100% of its weight made up of methyl methacrylate. Possible comonomers are, for example, alkyl acrylates with 1 to 8 carbon atoms in the alkyl radical or alkyl methacrylates with 2 to 8 carbon atoms in the alkyl radical, acrylonitrile and / or methacrylonitrile, styrene or vinyl esters of saturated fatty acids with 2 to 10 carbon atoms. In minor amounts, approximately up to 5% by weight, monomers with functional groups such as acrylic and / or methacrylic acid, their hydroxyalkyl esters or aminoalkyl esters can be involved in the synthesis of the methyl methacrylate polymer. The type and proportion of the comonomers are chosen so that the polymer is soluble in suitable organic solvents and in methyl methacrylate; for this reason, crosslinking comonomers with more than one ethylenically unsaturated, free-radically polymerizable group are unsuitable.
Methyl methacrylate polymers of 90 to 100% by weight of methyl methacrylate and the remaining part of lower alkyl acrylates with 1 to 4 carbon atoms in the alkyl radical are particularly suitable.

The methyl methacrylate polymer together with liquid, monomeric methyl methacrylate makes up a share from at least 80% by weight of the adhesive, preferably 90 to 98% by weight. In addition to methyl methacrylate other monoethylenically unsaturated monomers copolymerizable therewith, such as those which act as comonomers for the Methyl methacrylate polymers have been named, a limited portion, up to about 10% by weight of the total adhesive turn off.

The adhesive contains crosslinking monomers up to 7% by weight, preferably 0.5 to 5% by weight, in particular 1 to 3 wt .-%, especially multifunctional acrylic and / or methacrylic monomers. As networking components are bifunctional, trifunctional acrylic and / or methacrylic monomers and also more functional ones such as tetrafunctional Acrylic and / or methacrylic monomers can preferably be used. These are preferably ester functions, especially acrylic ester functions. Suitable multifunctional acrylic and / or methacrylic acid esters are derived from aliphatic polyhydroxy compounds with at least 2, preferably at least 3 and particularly preferably at least 4 hydroxyl groups and preferably 2 to 6 carbon atoms. Examples are ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, glycerol, trimethylolpropane, pentaerythritol, tetramethylolethane, Sorbitan. Examples of suitable esters are:

Glycol diacrylate and dimethacrylate, butanediol diacrylate or dimethacrylate, dimethylolpropane diacrylate or dimethacrylate, diethylene glycol diactylate or dimethacrylate, divinylbenzene, trimethylolpropane triacrylate or trimethacrylate or trimethacrylate, triethacrylate or triethacrylate, triethacrylate or triethacrylate, triethacrylate or triethacrylate, triethacrylate or triethacrylate, triethacrylate or trimethacrylate, , 4-butanetetraol tetraacrylate or tetramthacrylate, tetramethylolethane tetraacrylate or tetramethacrylate, 2,2-dihydroxy-propanediol-1,3-tetraacrylate or tetramethacrylate, sorbitan tetra, penta- or hexa-acrylate or the corresponding Methacrylates.
Mixtures of crosslinking monomers with two to four or more ethylenically unsaturated, free-radically polymerizable groups can also be used.

Known compounds are used as photoinitiators. Named as daylight photoinitiators above Compounds of the class of acyldiphenylphosphine oxides, especially benzoyldiphenylphosphine oxides, before all 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or 2,3-bornandione.

oder Irgacure® 369 und/oder Benzophenone oder Benzoine. Sie werden in üblichen Mengen eingesetzt, d.h. wenigstens 0,01 Gew.-% und vorzugsweise 0,1 bis 10 Gew.-%, insbesondere bis 1 Gew.-%, bezogen auf das Gewicht des Klebmittels.Preferred UV photoinitiators (Photoinitiatoren II) are diisopropylxanthogen disulfide or acetophenone compounds, such as. B. Darocur® 1173 of the formula

or Irgacure® 369 and / or Benzophenone or Benzoine. They are used in customary amounts, ie at least 0.01% by weight and preferably 0.1 to 10% by weight, in particular up to 1% by weight, based on the weight of the adhesive.

Other usual additives can also be used at Bedarl, e.g. UV protection agents, UV absorbers, stabilizers, Amines to cancel the oxygen inhibition when using 2,3-bornandione as daylight initiator, high-boiling plasticizers, etc.

Suitable plastics for gluing

Acrylic plastics are understood to mean polymers of methyl methacrylate which contain up to 50% by weight of other, so that radically copolymerizable monomers can be built up. The proportion is preferably of methyl methacrylate 80 to 100 wt .-%. The primary comonomers are alkyl esters of acrylic acid with 1 up to 4 carbon atoms in the alkyl radical as well as acrylonitrile and / or methacrylonitrile, styrene or maleic anhydride. Thermoplastic and thermoelastic malleable acrylic plastics are preferred; their viscosity number (according to DIN 53 727 or 51 562, part 1) is preferably in the range from 20 to 1,500 ml / g.

The molded parts made of acrylic plastic can be made with molded parts using the adhesive according to the invention made of other plastics, such as rigid PVC, cellulose esters, polystyrene, ABS plastics, polycarbonate or polyethersulfone be glued. Your Vicat softening temperature should not be below 70 degrees Celsius. Highly cross-linked plastics, which cannot be processed either thermoplastic or thermoelastic are less suitable. At least one of the plastics involved must be sufficiently transparent to the radiation used for curing in order to to be able to effect the curing in a short time. Clear plastics are preferred. With particular advantage the adhesives according to the invention used for gluing molded parts made of acrylic plastic together.

The adhesive according to the invention is also for the bonding of acrylic plastics with other non-plastic ones Materials such as glass, wood or metals can be used.

The adhesive process

One is used to glue a molded body made of acrylic plastic to another molded body made of plastic Layer of the adhesive according to the invention which is in contact with the moldings to be bonded, under which Exposure to radiation for which at least one of the moldings is transparent and which affects the photoinitiator has an activating effect, hardened.

As a rule, one of the plastic bodies to be bonded is coated with a layer of the liquid adhesive and assembled with the other plastic body as bubble-free as possible. You can also dry the parts join together and allow the adhesive to be drawn into the adhesive joint by capillary force. The glue line can be a Thickness from about 1 micron to several millimeters. The joined bodies will be in the desired one Position fixed and exposed to a suitable radiation to harden the adhesive layer. The exclusion oxygen or air is generally not required.

Incandescent lamps and tubes are effective radiation sources for sensitizing daylight initiators that emit light in the wavelength range of at least 400 to 500 nm, e.g. Daylight LS tube S25. UV light sources can also be used more advantageously for triggering the polymerization with the combination of photoinitiators I and II be used, e.g. the UV-LS tube TL09 or the UV-LS tube TL05 (blue light tubes).

The UV radiation used expediently has a maximum power in the range from 300 to 400 nm. Further Suitable radiation sources are black light fluorescent lamps, mercury vapor lamps, UV lasers and the like a power of about 4 to 2,000 watts. A radiation power of at least 10 mWatt / qcm is advantageous. Uncolored, Clearly transparent acrylic plastics have sufficient permeability to UV radiation so that they allow quick hardening. UV light sources with a high proportion of radiation in the wavelength range 400 to 500 nm are also sufficient as light curing sources with photoinitiator combinations I and II.

The adhesive in the glue line cures best at a temperature in the range of 0 to 80 degrees C. Higher Temperatures can evaporate volatile components, low temperatures can take longer to harden to lead. The adhesive joint fully hardens within 8 to 15 minutes under favorable conditions. The hardening can last longer if the radiation spectrum of the radiation source does not match the absorption spectrum of the initiator matches or if the power of the radiation source is low. Even with diffuse ambient light, it works within from about 60 to 80 minutes complete hardening. In general, there is no obstruction by atmospheric oxygen observed. Even exposed parts of the adhesive layer harden quickly and tack-free. The hardened adhesive layer shows residual monomer contents of about 3 to 6% by weight.

After the end of the irradiation, the bonded molded body can be processed further immediately. The invention The bond created meets the highest demands for resilience and weather resistance. A subsequent one Annealing can be an advantage. The adhesive wedge is high as it is for a polymerization adhesive The basis of methyl methacrylate / polymethyl methacrylate is to be expected: Monomers swell into the acrylic glass surfaces to be glued on. During the polymerisation of the bonded seam, a more homogeneous result is created by looping and grafting Material composite. The optical properties of the adhesive seam are optimal: It shows when selecting suitable initiators no yellow tinge and hardens with both fillet and butt-butt bonding without bubbles.

The high impact strength and tensile shear strength of the hardened adhesive joint allows the bonded molded body to process like a one-piece molding, e.g. by sawing, milling, drilling, grinding or by thermoelastic Forming when the bonded molded body itself is accessible to such processing.

EXAMPLES Example 1 (not according to the invention) Production of a polymerization adhesive

67.57 g of methyl methacrylate (MMA) are introduced into a 2 liter round flask made of amber glass with a saber stirrer and a reflux condenser. After adding 0.03 g of 4-methyl-2,6-di-tert-butylphenol and 32 g of polymethyl methacrylate (PMMA) molding material (Plexiglas® γ7N), the mixture is heated to 40 ° C. with stirring and stirred until the Polymer has completely dissolved. It takes about 5 hours. The solution is then cooled and 0.4 g of the photoinitiator Lucirin® TPO (BASF) are added and stirred in at a temperature below 25 ° C. and in the absence of light.
The resulting polymerization adhesive has a viscosity of 1 840 mPa s (25 degrees C)

Examples 2-4 Manufacture of polymerization adhesives

The procedure is as described in Example 1. In a departure from Example 1, the following amounts of methyl methacrylate and photoinitiators are used. example MMA Photoinitiators 2nd 67.37 g 0.2 g Lucirin® TPO + 0.4 g diisopropylxanthogen disulfide 3rd 67.17 g 0.4 g 2,3-bornanedione + 0.4 g diisopropylxanthogen disulfide 4th 67.17 g 0.4 g Lucirin® TPO + 0.4 g Darocur® 1173

Example 5

In a round bottom flask according to Example 1, 73.73 g Weighed in methyl methacrylate. Then 0.03 g 4-methyl-2,6-di-tert-butylphenol and 25.6 g Plexiglas® γ7 N molding compound added. After 5 hours Stirring at 40 degrees C will bring the mixture to 25 degrees C. cooled and 0.32 g Lucirin® TPO and 0.32 g Diisopropylxanthogen disulfide are stirred in.

Comparative example

The polymerization adhesive of the comparative example contains only one type II photoinitiator. The comparison with examples 1-5 shows the use of photoinitiator I according to the invention on the curing time:
As described in Example 1, 67 g of methyl methacrylate are weighed into a flask and 0.05 g of 4-methyl-2,6-di-tert-butylphenol and 32 g of Plexiglas® γ7 N molding compound are added. After stirring for 5 hours and cooling to 25 ° C., 1 g of diisopropylxanthogen disulfide is added and stirred in.
The polymerization adhesive has a viscosity of 1 890 mPa s (25 degrees C).

Determination of the curing time

The curing time is determined on a test bond. For this purpose, two sheets of 10 mm thick cast acrylic glass are glued together in a T-shape. The edge of the attached plate was previously beveled, so that a V-shaped adhesive seam results. With the help of a thermocouple in the glued seam, the time from the start of the irradiation until the temperature maximum is reached is determined. The hardness times determined in this way are a measure of the hardness times when acrylic glass is bonded. Adhesive according to the example Curing time (min) Lamp type illuminant 1 12th L25 2nd 18th TL05 2nd 17th TL09 2nd 19th L25 3rd 23 TL09 4th 10th TL09 4th 18th L25 5 32 L25 Comparison 6 43 TL09 Comparison 6 53 L25

TL05

Phillips Spezial-Leuchtstofflampe, superaktinisch Emission 310 - 470/ 550 nm

TL09

Phillips Spezial-Leuchtstofflampe, blacklight Emission 305 - 450/550 nm

L25

Phillips Weiß Universal 25 Emission 305 - > 700 nm

The lamp types used are:

TL05

Phillips special fluorescent lamp, superactinic emission 310 - 470/550 nm

TL09

Phillips special fluorescent lamp, blacklight emission 305 - 450/550 nm

L25

Phillips White Universal 25 Emission 305 -> 700 nm

Determination of the adhesive strength

The adhesive strength was determined as tensile shear strength according to DIN 53 283 (ASTM 3163-73) on test specimens made of cast Acrylic glass determined.

The adhesive from Example 2 was used. Lamp type illuminant Tensile shear strength (MPa) after gluing after tempering (5 hours / 80 degrees C) TL05 22 39 TL09 28 51 L25 30th 54 diffuse ambient light 36 52

Curing of bonds in diffuse ambient light

Two sheets of 20 mm thick cast acrylic glass were glued in a T-shape with a V-seam as described above. No fluorescent lamps were used for curing. Rather, curing takes place in normal daylight (diffuse ambient light). Example glue Curing time (min) Strength of the bond in a manual test 1 160 very good, cohesive break 2nd 100 very good, cohesive break Comparison 6 no curing

Claims (7)

1. A light-hardening polymerisation adhesive for acrylic glass, comprising a solution of a polymer mainly synthesised from methylmethacrylate in a polymerisable monomer which is mainly methylmethacrylate, characterised in that the proportion of methyl methacrylate polymers is 20-60 wt.-%, based on the weight of the adhesive, the proportion of methyl methacrylate polymers together with fluid, monomeric methyl methacrylate in the adhesive is at least 80 wt.-% and the adhesive contains up to 7 wt.-% of a crosslinking polyfunctional monomer, and in order to initiate photopolymerisation, the adhesive comprises a combination of at least one daylight-photoinitiator, in amounts of 0.01 to 10 wt.-%, which has at least one absorption band within the wavelength range of 340 - 500 nm, and one photoinitiator II which has at least one absorption band in the same wavelength range, the absorption bands of the two photoinitiators being at different wavelengths within this wavelength range.
2. A light-hardening polymerisation adhesive according to claim 1, characterised in that it comprises at least one daylight-photoinitiator in amounts of 0.01 to 1 wt.-%.
3. A light-hardening polymerisation adhesive according to claim 1 or 2, characterised in that it comprises a daylight-photoinitiator from the benzoyldiphenylphosphine oxide class.
4. A light-hardening polymerisation adhesive according to one or more of claims 1 to 3, characterised in that it contains 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and/or 2,3-bornanedione (camphorquinone) as the daylight-photoinitiator.
5. A light-hardening polymerisation adhesive according to one or more of claims 1 to 4, characterised in that it comprises diisopropylxanthogene disulphide as the photoinitiator II.
6. A process for bonding a moulded article made of acrylic plastic material with another moulded article made of plastic material, in which a layer of adhesive, which is in contact with the moulded articles to be bonded, is hardened under the effect of radiation, in respect of which at least one of the moulded articles is transmissive and which leads to an activating effect on at least one of the photoinitiators, characterised in that the adhesive used is an adhesive according to claim 1, 2, 3, 4 or 5.
7. A process according to claim 7, characterised in that moulded articles made of acrylic plastic material are bonded to one another.